Friendly Voice

Download extension

Makes Google Voice a little friendlier when you type more than 320 characters.Google Voice can send out messages of up to 440 characters, spread out over 3 different texts. When you get to the third text, Google adds a snarky little message saying "Really?". This app replaces the quip with an an informative character countdown. It lets you know how many characters are remaining so you can plan your message accordingly.

You can look at it, run it on your own, or fork it from here:
https://github.com/KyleMit/FriendlyVoice

Also includes ability to resize message box area and ability to incrementally show hidden messages